Inbreeding, such as a dog becoming pregnant by her brother, significantly increases the risk of health problems in the puppies. This is because it concentrates recessive genes, potentially leading to genetic defects.
Increased Risk of Health Problems in Offspring
The primary concern with a dog becoming pregnant by her brother is the increased likelihood of genetic disorders in the resulting litter. This is due to the higher probability of both parents carrying the same recessive genes responsible for inherited diseases. These puppies might exhibit various health issues, potentially impacting their lifespan and quality of life. (Reference: In general most dog breeders would not choose to do such close inbreeding. You might double up on unsuspected recessive traits and have some pups with health problems.)
Potential for Smaller Litters
In some instances, inbreeding can result in a smaller litter size than expected. This occurs because genetic defects can cause some fetuses to not survive to term. (Reference: You may also get a smaller than normal litter if some of the fetuses don't make it to being born due to defects.)
Inbreeding and its Consequences
Inbreeding, or close breeding, is a common practice in some animal breeding programs to maintain certain desirable traits within a bloodline. However, it carries significant risks. Closely related parents share a large portion of their genetic material, increasing the chance of homozygous recessive genes manifesting as health problems in offspring. While some puppies might be healthy, the overall risk is significantly increased. (References: Various Quora and Reddit threads discuss this risk, highlighting potential for health problems and smaller litters. One Reddit user mentions that even with inbreeding, the outcome isn't guaranteed to be negative, but the risk is significantly increased.)
What to Do
While the mother dog will likely experience a normal pregnancy, the welfare of the puppies is a serious concern. Consult a veterinarian for guidance on managing the pregnancy and evaluating the health of the puppies after birth. Spaying the mother dog after this pregnancy is generally recommended to prevent future inbreeding. (References: Several sources suggest spaying the mother dog to prevent recurrence. One source states that even if the puppies appear healthy, spaying should still be considered.)
